In general, coated steel plates ("the galvalumes") are widely used for ornamental wall and roof materials in construction because it is corrosive resistant, durable, and superior in heat reflection. Minimizing the size of spangle particles that form on surface of a coated steel plate provides the plate with fine appearance and improves its corrosive resistance, durability, and ease of handling, which are very important considerations in this technical field.
Traditionally the galvalume has been manufactured by the following process. A steel plate is passed through a pot with melted alloy, coating composition, comprising of Al 55% by weight, Zn 43.4% by weight, and Si 1.6% by weight. Amount of coating put on the steel plate is controlled by a method of air wiping; then quenching is accomplished by a means of cooling. The size of spangle particles on surface of the coated steel plate depends on efficiency of the cooling, more efficient the cooling smaller the spangle particles.
However, the existing quenching method, i.e., the method of cooling, cannot guarantee uniform minimization of spangle particles because it depends on the quenching capacity, the length of quenching equipment, the temperature of the pot, and the line speed for production of the galvalume. It is very expensive to increase the cooling capacity to improve effectiveness of quenching that is needed to minimize the size of spangle particles; consequently, the existing galvalume production method is inefficient.